Polyvinylamines
Polyvinylamines and the method of making are well known in the literature. Polyvinylamines are typically prepared by partially hydrolyzing N-vinylformamide polymers. See for example, U.S. Pat. Nos. 4,421,602, 6,576,086 6,616,807 5,290,880 6,159,340, 7,034,068 and 6,797,785, herein incorporated entirely by reference. The formed polyvinylamines are known for enhancing retention and drainage in the formation of paper. Faster drainage of the stock on the papermaking machine enables the speed of the machine and hence production to be increased.
Fuctionalized and crosslinked polyvinylamines are also known in the literature. For example, U.S. Pat. No. 7,090,745, herein incorporated entirely by reference, describes a hydrophilic polymer containing primary and/or secondary amines and at least one sugar containing a reducible function such as an aldehyde or hemiacetal. The resulting hydrogels are alleged to increase paper strength.
U.S. Pat. No. 5,281,307 discloses a crosslinked polyvinylalcohol/vinylamine. The crosslinked copolymer is added at the dry end step of a conventional papermaking process.
U.S. Pat. No. 6,824,659 discloses combinations of polyvinylamine with a complexing agent in order to improve the wet strength properties of paper. The complexing agent may be a glyoxalated polyacrylamide.
U.S. Publication App. Nos. 2006/0065380 and 2004/0118540 also disclose combinations of polyvinylamine with a glyoxalated polyacrylamide for purposes of improving the wet strength properties of paper.
Glyoxalated Vinylamide Polymers
The use of synthetic water-soluble polymers as wet end additives for the strengthening of paper and paperboard is widely practiced. The use of cellulose reactive water-soluble vinylamide copolymers as paper strengthening agents is also common. One particular class of vinylamide polymer strength aids includes vinylamide polymers which are modified with glyoxal in such a way as to be thermosetting.
Glyoxalated vinylamide polymers are described for example in U.S. Pat. Nos. 3,556,392, 4,217,425, 4,605,702, herein entirely incorporated by reference.
PCT Published Application No. 2006/016906 describes a cationic vinylamide crosslinked polymer which is treated with a cellulose reactive agent such as glyoxal to impart strength to paper.
U.S. Pat. Nos. 4,954,538, 5,041,503 and 5,320,711, herein incorporated by reference, teach microparticles of cross linkable, glyoxalated-polyvinylamide prepared by reverse phase microemulsion polymerization and describe adding glyoxal to the micro emulsion polymer to form a glyoxalated polymer.
U.S. Published Application No. 2008/0064819, herein incorporated entirely by reference teaches an aqueous reaction of a cellulose reactive agent such as glyoxal with polyvinylamide. The reaction takes place at low polyvinylamide concentrations. The described reaction conditions give cellulose reactive polyvinylamide adducts which are shown to give improved wet and dry strength in paper.
The inventor has discovered that the reaction of polyvinylamine with at least a dialdehyde produces a functionalized polyvinylamine which gives paper or board of improved wet and/or dry strength.
Furthermore, it has also been discovered that functionalizing both a polyvinylamine and a polyvinylamide with a cellulose reactive agent such as glyoxal simultaneously gives at least first and second adducts which when applied to a furnish or applied as a paper or board coating give unexpected wet and/or dry strength.
Additionally, it has also been discovered that the cellulose reactive functionalized polyvinylamide disclosed in U.S. Published Application No. 2008/0064819 when combined with polyvinylamine (unfunctionalized) and simultaneously added (or added simultaneously but separately) to a furnish or coated onto a paper or board will also give improved wet and/or dry strength to the paper or board.
A premixture formed from polyvinylamine (unfunctionalized) with the glyoxalated polyvinylamide product according to U.S. Published Application No. 2008/0064819 may boost the performance of the glyoxalated product especially in papermaking systems containing high amounts of anionic trash (pitch, stickies, white pitch etc.).
It is also believed that premixing of polyvinylamine (glyoxalated or unglyoxalated) with standard glyoxalated polyvinylamide (i.e. U.S. Pat. Nos. 3,556,392, 4,217,425, 4,605,702) before addition to the furnish in a papermaking process also boosts performance in papermaking systems containing high amounts of anionic trash.
Although not wishing to be bound by theory, it is possible that the highly charged cationic polymer (polyvinylamine) when combined with a lower charged cationic polymer (such as a cationic glyoxalated polyvinylamide) “blocks” anionic trash in the papermaking system from interfering with the lower charged cationic polymer, so that the lower charged cationic polymer may work more efficiently.